Wireless transmission of telegraph impulses



Jan. 9, 1934. D. THIERBACH 1,942,580

WIRELESS TRANSMISSION OF TELEGRAPH IMPULSES Filed April 22, 1930 F139? GENE/EA TO E5 F/LTEES To JEPAEATE JPEECH TELEGEPH EL EPHo/v F BE UE/VC E5 INVENTOR DIETWA IERBACH BY 7 wbn/ ATTbRNEY Patented Jan. 9, 1934 UNITED STATES WIRELESS TRANSMISSION IlVIPULSES or TELEGRAPH Dietwald Thierbach, Berlin, Germany, assignor to Siemens & Halske Aktiengesellschaft, Siemensstadt, near Berlin, Germany, a corporation of Germany Application April 22, 1930, Serial No. 446,326, and in Germany April 25, 1929 3 Claims. (Cl. 2508) On transmitting wireless signals, additional disturbing voltages and fiuctuations in sound volume (fading) must often be taken into account at the receiving station.

According to the invention, a reduction of the influence of the disturbing voltages can be obtained in transmitting the telegraph signals as double-current signals on two carrier waves or on one carrier wave with two modulation frequencies and in applying them at the receiving station to a compensation (differential) circuit. In such a method, one of the frequencies produces a positive current at the receiving station and the other a negative current. Both currents may be sent, for instance through a differential relay which is not operated as soon as a positive and a negative current occur at the same time. It results therefrom that disturbances existing on both waves do not give rise to false signals. The elimination of disturbances will be the more complete the nearer the two telegraph frequencies are lying together.

Such a telegraph system furthermore offers the advantage that it permits of carrying out a simple fading regulation. Since a double-current signal at the receiving station always involves the existence of a signal current, the amplitude of these signals may be taken as a measure of the attenuation inherent in the transmission path. This condition can be utilized for the purposes of an automatic attenuation regulation, which fact is of further advantage in the case of simultaneous telegraphy and telephony. The special control frequency usually employed for fading regulation can then be dispensed with, if the telegraph frequency is used for this end.

Figures 1 and 2 illustrate a constructional example of the invention, Fig. 1 representing the transmitting station and Fig. 2 the receiving station.

The two generators G1 and G2 which produce the adjacent frequencies f1 and f2 are, through the key relay RT, alternately applied to the transmitter S which emits a carrier frequency. The band-pass filters K1 and K2 confine the telegraph spectrum in such a manner, that frequencies interfering with the telephone set, consisting of the transmitter M and the input amplifier W, are screened out.

The frequencies emitted in this way are received by means of a receiver E, which is followed by a control amplifier RV common to telegraphy and telephony. The incoming current passing through the control amplifier, is branched off to the filters K3 and K6. The filter K3 rejects the speech frequencies and enables the telegraph frequencies to reach another current branching tap, in the two branches-of which are inserted filters K4 and K5 each letting through one of the two telegraph frequencies. The telegraph frequencies separated in such a manner from one another are rectified by means of de- 35..-

tectors G11 and G13 and led to the differential relay set B of a given constructional design. If G12 is energized, a direct current flows in the direction of the arrow a, if G13 is energized, in

the direction of the arrow b. In the case of a 1 simultaneous operation, owing to interfering currents, no signals will therefore be received, on account of the balance in B, (provided the interfering impulses have the same amplitude as the signals). telegraph frequency current is branched off and after having been rectified in the detector G11, led to the control amplifier RV, in order to effect an amplitude regulation in a well-known man- Behind the filter K3, part of the ner, for instance, by means of a potential shift of its grid.

The filter K6, which is so designed as to enable the telegraph frequencies to be rejected and the speech frequencies to be transmitted, permits of carrying the speech currents on to the receiving set H.

The control amplifier RV common to the telegraph-and speech frequencies, is used simultaneously, for fading regulation on transmitting speech, since it is controlled by means of the permanently existing telegraph frequency signals.

I claim:

1. Means for receiving signals composed of double current impulses at different frequencies and continuous voice modulated oscillations including,

rectifiers, and a rectifier having its input termi- I nals connected to the output of said amplifier and its output terminals connected to the volume control means in said amplifier.

2. Means for receiving signals composed of double current impulses of different frequencies comprising, signal absorbing means tuned to a band of frequencies, an amplifier connected with said absorbing means, said amplifier including automatic volume control means, a filter circuit signal responsive means, said amplifier including volume control means, a plurality of filter circuits connected with said amplifier, an indicator connected with one of said filter circuits, a rectifier connected with the output of another of said filter circuits, means connecting said volume control means with the output of said rectifier, a plurality of filter circuits connected with said last named filter, rectifying means connected with each of said last named filter circuits, and a difierential recording means connected with said last named rectifiers.

DIETWALD TI-IIERBACH. 

